The objective of this research proposal is to determine the reactivity of 4-oxononenal (4ONE), a major product of lipid peroxidation, toward peptides/protein. 4ONE is structurally analogous to the known cytotoxic lipid aldehyde 4-hydroxynonenal (4HNE) but is likely more reactive because of its chemical structure. Protein modification by 4HNE has been characterized and is thought to be an initiating factor in the pathogenesis of human diseases (e.g. atherosclerosis); however, the adduction of peptides/proteins by 4ONE has not been studied or even demonstrated. In order to fulfill the objective of this research proposal, the following working hypotheses will be tested: 4ONE covalently modifies peptides and proteins with residue specificity and can inhibit enzymes that metabolize 4HNE; furthermore, 4ONE generated in the mitochondria from lipid peroxidation can modify mitochonidrial proteins/enzymes important in respiration and metabolism. To test the hypothesis, experiments will be performed to identify peptide residues adducted by 4ONE, characterize the preference of the compound toward specific amino acids, and determine the chemical structure of 4ONE adducts. Work will be done to ascertain whether 4ONE inhibits enzymes important for metabolism of 4HNE. Furthermore, experiments will be conducted to determine whether 4ONE generated via mitochondrial lipid peroxidation adducts mitochondrial enzymes/proteins important in respiration and metabolism. Completion of these aims will provide scientific data to achieve the objective of the research proposal and assess the toxicological/physiological significance of protein adduction by 4ONE.